Method and device for making biased spiral wound tension springs



Jan. 24, 1950 A. DE VRIES ETAL METHOD AND EVICE FOR MAKING BIASED SPIRAL UND ENSION SPRINGS Filed Dec. 3, 1946 Inventors:

ham deVries, s de Vries,

Attorney Patented Jan. 24, 1950 UNITED STATES PATENT OFFICE Abraham de Vries and Louis a; Vries,

Amsterdam, Netherlands Application December a, 1946, Serial a. 713,686 3 Claims. (01. 153-67) The manufacture of a biased spiral wound tension spring has hitherto taken place in such -a way that the spring wire is wound round a mandril, a certain amount of torsion being imparted to the wire at the same time.

Because during the winding of the wire some flowing of the material will take place-as a result of the permanent deformation to be imparted to it--the simultaneously evoked torsional stress will largely be undone. Consequently the result is usually an only slightly biased tension spring, the bias being mostly spread unevenly over the spring too.

In order to improve the manufacture of this kind of tension springs according to the invention the sides of the windings of a preformed, strainfree spiral spring, which sides originally do not face each other, are, laid against each other by rewinding the spring, with an at least temporary increase or decrease of the diameter of the spring.

The preformed spiral spring may be made of soft material and be tempered before being moulded into its final form.

The rewinding of the preformed springs may be combined with the preforming itself, so as to avoid long preformed springs and the spring when being wound can be immediately rewound.

The device for carrying out this method may, according to the invention, consist of means for radially supporting the preformed spring and an axially movable and rotatively supported carrier, positioned coaxially in respect of these means, with a clamping device fitted to it for gripping the leading end of the preformed spring.

To illustrate the invention, an embodiment of the device and the method to be carried out with it shall be described with reference to the draw- According to the drawing the embodiment of the device consists of a frame I, in which the carrier 2 is supported rotatively and axially movably. At its one end the carrier is provided with a clamping device consisting of a clamping cap 4 which may be set tight with a nut 3 for securing one wire of the spring to the carrier 2.

concentrically round the carrier the frame I is provided with a number of supporting rollers 5 which are freely rotatable round the shafts I fixed to the frame I by means of a nut 6. One of the supporting rollers 5 is provided with a circular collar 8, extending beyond the surface of the supporting roller over a distance about equal to the thickness of the spring wire to be treated.

The operation of the device is as follows:

Of a preformed spiral spring 9 the end turned towards the device is secured to the carrier 2 with the help 'of the clamping cap 4, said carrier 2 being pulled back in upward direction so far. that the clamped end of the spring lies opposite the collar 8 of the supporting roller 8 and the adjacent portion of the spring is enclosed and supported by the rollers 5. Next the carrier 2 is rotated in the direction of the arrow and at the same time moved axially downwards inside the preformed spring so that at each revolution it covers a distance equal to the thickness of the wire of the spring to be rewound. By this movement of the carrier 2 and under the influence of the pressure exercised by the collar 8 of the supporting roller the pitch of the preformed spring is entirely undone and the windings are laid against each other with the sides which originally did not face each other.

During this winding a torsion comes into existence in the spring wire, which ultimately finds expression as bias in the finished spring.

Because this torsion is only imparted to the spring wire after said wire has already received its spiral form, the torsion will not be unnecessarily affected by overloading of the wire material as this need no longer be bent unnecessarily.

By selecting a suitable pitch of the preformed spring the bias of the finished spring may be adjusted at will, which bias may be raised to the maximum admissible bias.

The application of the method according to the invention further offers the important advantage that now a biased spiral spring may be made of soft wire too by first winding such a wire into a preformed spiral spring, tempering said spring and next making it into a biased spring by rewinding it in the manner described.

When starting from hard wire the advantage is obtained that finally a spiral spring comes into existence in which the bias is evenly spread over the entire length of the wire.

In a spring made according to the invention the desired bias may be accurately predetermined.

We claim:

1. A method for making a biased spiral wound tension spring comprising forming a preformed strain free spiral spring the convolutions of which are not in contact with one another and said convolutions having one direction of turn, securing an end of said preformed spring on a rotatable member and rotating said member inside the coil of the preformed spring in a direction opposite to that of the turns of the preformed spring and forming thereon a coiled maintaining the internal surface of the turns of the preformed spring inclose contact with the external surface of the spring having the reversed turns.

2. In a method as claimed in claim 1, said preformed spiral spring being constructed of a soft wire and wherein the wire is tempered before being shaped in its final form.

3. Apparatus for forming a spiral spring having the convolutions thereof in contact with one another comprising a frame, a carrier member rotatably mounted in said frame and having a portion thereof extending outwardly from said frame, a clamping cap on a free end of said carrier member, two spaced supporting rollers rotatably mounted on said carrier member and extending parallel to the said carrier member, a circular collar on one said supporting roller having a larger diameter than said roller, said rollers being spaced from said carrier approximately twice the diameter of the wire to be formed into a spiral spring. and said collar being spaced from said carrier 9. distance approximately equal to the diameter of the said wire, the said carrier member being axially movable in said frame.

- ABRAHAM DI vms.

LOUIS n: VRIES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,505,347 Hoyt Aug. 19, 1924 1,774,424 Deal Aug. 26, 1930 2,142,865 Zabel Jan. 3, 1939 2,173,096 Campbell Sept. 19, 1939 2,248,149 Wilson July 8, 1941 2,325,462 Arthur July 27, 1943 2,439,272 Sholtis Apr. 6, 1948 FOREIGN PATENTS Number Country Date 268,685 Great Britain Apr. 7, 1927 

